Fuse plug



Nov. 17, 1936. F. J. MGHUGH 2,0601519 S PLUG Filed Nov; 9, 1933 iigwyg I /%//////W a Q1 wa N MJ- Mcf/@w yliaten'ted Nov. 17, u

2,060,319 rusa PLUG Frank iJ. McHugh, Chicago, Ill., assigner to The Shake-,Back Corporation, Chicago, Ill., a corporation of Illinois Anseeuw Nevembee e, ma, segua Ne. man

.1o einen (c1. zoe-11a) My invention relates in general to protective devices for electrical circuits andhas more particular reference to safety breakers or cut-out devices for interrupting a circuit when the same 5 becomes overloaded, the inventionccmprising iniprovements in and a continuation of the invention disclosed in my co-pending application, Serial Number 678,404, filed `June 30, 1533, for

Fuse plug.

l An important object .of the invention is to provide a breaker of the type having a liquid currentcariying medium which, when overload conditions prevail, is adapted for expulsion from normal current-carrying position to thereby rupture l and open the protected circuit and the invention further contemplates provision Vfor the return of the current-carrying medium to current-carrying position after expulsion in order to render the device again effective for further use in protectconductor of fusible material in series relation Y withl the liquid medium when in current-carrying position, said fusible material being adapted to 35 be melted to thus interrupt the circuit upon overload in the protected circuit in the event that the liquid medium, for any reason, falls to be expelled. from circuit-making position.

Another important object is to provide a cir 40 cuit-protecting breaker, in. which a conductor g medium is-normally positioned in a channel or, duct from which the medium is expelled'in breaking the protected'circuitand to provide means to prevent enlargement of the duct or channel .45 and consequent increase in 'the maximum current-carrying capacityof the conductor medium without expulsion as a result of arcinggin the channel upon interruption of the protected circuit.

so A runner object atelier-m the or duct by stacking perforated plates .in-align-v ment.

Another important object isto form the arcing duct or channelof arc-resisting material. 5.5 Another important-object is to Aformthe arcresisting-*duct or channel of stacked disks of nbre, lava.4 asbestos'. or similar heat and arc-resisting materials having aligned perforations forming the arcing channel, and a further object resides in forming at least one ofthe disks of metal, as, s for instance, steel, whereby to assist in retaining the liquid-,current-carrylng medium in4 circuitmaking position inthe channel or duct.

Another object is to utilize mercury as the liquid-current-carrylng medium and a further object is to form at least a part of the walls of the channel or duct, in which the mercury extends when in circuit-making position, as a zone of material attractive` to mercury whereby to utilize surface tension and the adhesive effect betweenthe mercury and the material forming the channel zone to' assist in Vretaining the mercury in circuit-making position in the channel or duct. e

Another ,importantobiect resides in the simm plified construction. ofthe cut-out device, the same being inexpensive and easily manufactured.

Another important object resides in the facility with which the several parts of the device may be manufactured and assembled to form a commercially saleable fuse. i z

A further object is vto, provide an electrical circuit breaker or fuse, which may be used repeatedly and substantially indefinitely to interrupt overloaded-circuits.

Another important object'is to provide an electrical circuit breaker or fuse comprising a sealed channel having an enlarged portion forming an expansion chamber and a duct or relatively restricted channel of substantially capillary character opening into the expansion chamber through a perforated terminal member, the remote end of said duct or restricted channel having 4a second terminal member in spaced relationship and insulated from the perforated ter- 40 minal member and the duct or channel contain- ,ing a quantity of liquid current-carrying medi- 4"um, preferably mercury, sufficient to lflll the restricted channel and to form an electrical connection between said spaced terminal members 45 whereby, when the circuit is subjected to normal conditions, current may travel through the liquid 4emma between ma spaced terminals and when forated terminal member, into the expansion chamber.' thus interrupting the circuit between ,the terminal members. 'f'NumerousfOther @im "nd advantages wm be u apparent from the following description, which,

taken in connection with the accompanying drawing, disclosespreferred embodiments of the invention.

Referring to the drawingz. Figure 1 is a sectional view takenI through a housing forming a part'of a device embodying my present'invention;

Figure 2 is a sectional view through a shell adapted' for assembly on the housing shown in Figure 1 in building a device embodying the present invention;

Figure 3 comprises perspective views of ele-i ments adapted for assembly within the housing kai shown in Figure 1 in forming a device embodying the present invention,the parts shown in Figure 3 being illustrated inthe relative positions occupied thereby in the complete assembly;

Figure 4 is a, sectional view taken through a device embodying the invention, showing the several parts in assembled position; and

Figure 5 is a sectional'view illustrating a modied construction.

To illustrate my invention, I` have shown on the drawing a circuit protector of the character commonly termed a blow-'out fuse, and although my invention is not necessarily restricted to any particular fuse type, I have shown a plugform particularly well adapted for use in receptacle sockets, such as are commonly used in commercial power circuits. The invention, however,

- may be embodied in other fuse forms, as, for inbe normally arranged to provide a liquid currentcarrying column extending between spaced terminals exposed in said channel or duct to thereby form an operative current-carrying path between the terminals. connecting the spaced terminals in an external circuit to be protected by the device against overload conditions. When the circuit becomesoverloaded, the liquid-carrying medium becomes heated because its maximum current-carrying capacity is exceeded and the .liquid is expelled from the substantially capillary duct or passage into an expansion chamber provided for the purpose. The protected surface is thus interrupted intermediate the spaced terminals and any arcing, which may occur upon the interruption of the circuit, is confined inthe channel between the terminals exposed therein. By properly. manipulating the device, as by shaking it, after recondition the fuse for further use as a circuit-g,

protecting device.

It lwill be obvious to those skilled in the electrical art that the size of the liquid column in the restricted duct or channel, between tlie electrodes,

determines the maximum amount of currentwhich may pass through the liquid column without causing the same to become overheated and thus be expelled into the expansion chamber; that is to say, the size of the restricted Means is also provided for causes the liquid to be ejected and the circuit broken. I have observed in connection with the devices illustrated in my aforesaid co-pending ap. plication, that the arcing,`which occurs in the restricted channel when the circuit is interrupted,

device during its useful life, I now propose to' form said channel of suitable materials, which will resist arcing in order that enlargement of the arcing channel may be substantially prevented and the fuse have substantially constant capacity throughout its eective life, which is highly desirable in electrical circuit breakers.

The embodiment shown in the drawing to illustrate my invention comprisesa circuit breaker I I, comprising a housing I3 of any suitable insulating material and preferably a moldable composition, such as the reactive product of phenol and formaldehydel with or without the addition of suitable fillers. A suitable materials, such as porcelain, may be utilized in forming the housing I3. The housing is formed with a preferably centrall bore or channel forming a chamber I5 open at one end ."of thehousing and closed in any suitable fashion at the opposite end of the housing. The housing also is preferably cylindrical, the chamber I5 being formed axially therein. Within the chamber I5, means is assembled to provide a pair of spaced terminals Il and I9 and a vrelatively restricted arcing channel communicating with both terminals and opening through one into an unrestricted portion 'of the chamber I5, which forms an expansion space or chamber preferably in the closed end of the chamber Il. The `terminal Il is preferably located substantially midway between the ends of the chamber I5 and the terminal I9 is positioned in the open end of the cham-- ber and forms a chamber seal. The terminal I1 also is formed with a central perforation 2| therethrough, said perforation preferably having a bell-shaped or widened mouth' opening toward the expansionspace in the -closed end of the chamber I5. The means forming the duct'or restricted channel is arranged in the chamber I5 between the terminals I1 and I9 and comprises arc-resisting material positioned in the chamber I5 and having the channel 23 formed therein.

said channel23 communicating at one end with the perforation 2i of the terminal I'I and at the other end with the terminal I9. The chamber Other molding compositions or other,`

I5 also contains a quantity 25 of suitable liquidv current-carrying material, such as mercury, sufficient to ll the restrictedchannel 23 and form a column 'contacting the surface of the terminal'- I '9, which is exposed at one endof the restricted channel 23 and extending through the'opening 2l Vof the terminal I1, whereby to complete a' rupturable electrical circuit between said"termi' nals through the lrestricted channel 23. The

housing I3 also carries means whereby the ter' m'inals Il and I9 maybe connected-in an external` electrical circuit to be protected.

In the illustrated embodiment, the terminal I8 is electrically connected withmeaxis formingV a contact stud 5I exposed at one end of the hous-f' vided with screw threads for engaging the other contact of a standard fuse receptacle and connector means 29 carried by the housing is provided for electrically connecting the `terminal shell 21 with the internal terminal I1. Obviously any suitable expedient may be employed for electrically, connecting the terminals I1 and I9 in an external circuit.

One of the important features of my .present invention resides in the simplicity of construction facilitating assembly whereby the circuit breaker or fuse of my present invention may be easily andcheaply manufactured. To this end, the connecting member 29, as shown in Figure 3 of the drawing, is 'preferably formed as a strip of suitableelectrical conducting material, such as copper, having a portion curled to form a ringlike terminal seat 3i and a tail 33 extending radially outwardly of the ring-like portion. 'I'he ring-like portion 3l preferably has an internal diameter' equal to the diameter of the chamber I5 as originally molded in the housing I3 and the connector 29 is preferably molded in the shell with the inner surface ofthe ring-like portion 3l lying flush with the inner walls of the chamber I5, the tail 33 extending radially through the walls of the housing with its end exposed on the outer siufaces of the housing I3 so vthat the shell 21, after being assembled on the housingmay be soldered or otherwise electrically connected to the exposed end of the tail. The tail also is preferably provided with notches 35 in its opposed edges to assist in firmly anchoring the member 29 in the walls of the molded housing. The terminal-I1 is preferably formed as a disk 36, the outer diameter of which is slightly greater than the bore of the chamber IB and the bore is enlarged as by reaming from its lower end to permit the terminal I1 to be inserted and pressed snugly into place 'within the ring-like portion 3| to make a good electrical connection therewith. It is desirable to introduce the current-carrying fluid 25 into the channel after the Isame has been reamed but before the disk 33 is inserted. It is not, however,` necessary to form the terminal I1 and connector 29 as separate pieces. They may be combined and formed as an integral element'if desired, but I prefer to form the parts as shown for the sake of convenience in manufacture and assembly.

In reaming out the chamber I5, I also ream the inner surfaces of the ring-like portion 3l to provide smooth finished surfaces to contact the sides of the terminal I1 and to provide a flange 31 upon which the terminal may bear in an axial direction and by which the terminal may be held in. place. Between the terminal I1 and the terminal I9 closing the open end of the bore I5, I arrange means forming a channel lining of arc-resisting means, such as horn fibre, lava, porcelain, asbestos,jand the like, arranged in the form of disks having central perforations to facilitate manufacture and assembly, and to increase'the mechanical strength ofthe liner. The disks, forming the arc-resistant channel lining are of uniform diameter and have central perforations which. Iwhen-'the disks are assembled in the chamber, are in alignment and form the restricted arc-resisting channel y 23.

I prefer to utilize a bre vdisk immediately fer to employ a disk 43 of somewhat greater width with a slightly smaller central perforation,

and to make the disk of highly arc-resisting material. By restricting the channel 23 at the central perforation of the disk 45, the arc may be made to start at this point and the disk is made of highly arc resistant material where the most destructive eifect is encountered. Y

The terminal I9 may be of any suitable or convenient form and is anchored firmly in the open end of the channel I3 after the terminal I1 the disks being snugly compressed by and between the terminals i1 and I9 and the edges of the terminal disk 39 being pressed snugly against the flange 31 of the ringlike holder 3l. I prefer, however, to form the terminal I9 as a preferably copper disk 41 of a size adapted to ilt into the reamed channel next to the disk 4l in position to close the end of the channel 23, the disk 41 being preferably formed with a central depression or socket 49in position to extend across the end of the channel 23 to aiford increased electrical contact with the fluid 23 when the same is' in the channel.

A contact stud 3| is secured in the end of the channel to hold the various disks in place and the stud extends outwardly of the open end of the channel to 'providean electrical connection between the disk 41 and the contact of a receptacle in which the device may be mounted to connect the device in `an external circuit. 'I'he plug may be fastened in the end of the channel in any convenient manner, although I prefer to anchor the plug in place by fastening it either by threadand disks 39, 4I, 43, and 43 have been assembled,

ing, as shown in Figure 5, or preferably .by

crimping it, as shown in Figure 4, in a holding collar which is preferably mounted in the housing as by being molded therein at the open end of the channel. the stud and collar for this pur-- of the channel. also is preferably beveled as at 59 to accommodate a sealing washer 6I, preferably of soft material, such as lead, whereby to seal the space between the stud and its encircling sleeve 59 and prevent the escape of mercury or mercury vapor from the chamber i5 during the operating life of the device. i l

It will be noted that the space in the chamber on the side of the terminal I1 opposite from the restricted arc-resisting channel 2 2, affords an enlarged expansion space into which the mercury 25 may pass through the central perforation 2| of the terminal I1 fromthe restricted duct or channel in order to interrupt the circuit betweenthe terminals I1 and I9 when overload conditions prevail; that is to say, when a current in excess of the maximum current-carrying ca-` pacity of the mercury column in the duct or channel 23 is flowing between the terminals I1 and I9. After the mercury has been so' expelled, the small size of the channel will normally pre- -vent the column from re-entering the channel 23 to re-establish the circuit. The mercury may. however, be returned tol circuiti-making position by simply shaking the device to` shake the mer.

cury down into the duct or channel 23 after which the surface-tension of the mercury on the terminal I1 and its adhesion on thesteel washer 4Iwil1causelt toremaininplace until again expelled into the expansion space as a `result of excessive current inthe mercury column.

`The connector, if desired, may be made of fusible material, such as lead, and the notches 35 may be arranged in the -tail I3 in such a way as to constitute the tail a fuse link in series with the i mercury column in the channel 23.y The fuse link may be formed to carry, without fusing, slightly more current than that at which the mercury column should be expelled from the channel 23 so as to give protection in the event that, for some reason, suchV as eventual enlargement of the bore of the duct or channel 23the mercury column-is not expelled when rated overload conditions prevail. Even where arc-resisting materials are employed, the channel 23 may eventually become enlarged to' such an extent that the current-carrying capacity of 'the enlarged mercury column becomes greater than the maximum rat.- ing of the device. Under such circumstances, the connector 29 itself is adapted to melt away and permanently disable the device.

It is thought that the invention and numerous of its attendant advantages will be understood from the foregoing description .and it is obvious that numerous changes may be made in the form, construction, and arrangement of the several parts without departing from thev spirit or scope of my invention orl sacricing any of its attendant advantages; the forms herein de scribed being preferred embodiments for the purpose of illustrating my invention.

Having thus described my invention, what I.

- least one of said electrodes having a perforation through which the mercury may escape from the duct to a remote part of the housing and may be returned through the perforated electrode I so rro

into the duct. y

2. A circuit breaker of the character described comprising a pair of `spaced electrodes and an insulating body having a channel in which said electrodes are mounted, one electrode being embedded in the body atv a point intermediate the ends` of the channel and the other electrode serving to close an open end of the channel, said channel forming an expansion space adjacent one of said electrodes, a stack of disc-like elements having perforations and disposed-in said channel between said electrodes with the perforations of -the several discs in alignment and defining a duct communicating with said electrodes and opening into said expansion space and a vliquid-current-carrying medium adapted to enter said duct and form a current-carrying circuit between said electrodes and, when excessive current conditions prevail in said path, to be expelled from said duct into said expansion space in order to interrupt the current-carrying cir.- cuit between said electrodes, said duct and expansion space being arranged so that themercury may be returned from the duct into Athe channel in order to reset the breaker.

3. A circuit breaker of the character described comprising a pair of spaced electrodes and an insulating body having a channel in which said 2,oso,s19

electrodes are mounted, a connector embedded in said body and having a portion extending to and exposed on the sides of the body and a portion forming an annular seatA exposed in the .channel substantially mid-way between its ends,

said channel forming an expansion chamber on one side of said seat and having an end opening atan end of the body on the other side of the seat, acentral electrode comprising a disk having a central perforation mounted in lsaid seat, said perforation wideningl toward saidexpansion,

expansion space and a liquid current-carrying medium adapted to enter said duct and form a current-carrying circuit between said electrodes, and, when excessivecurrent conditions prevail in said path, to be expelled from said duct into said expansion space in order to interrupt the lcurrent-carrying circuit between said electrodes.

4. A circuit breaker of the class described.

comprising a body formed with a socket having" a closed and an open end and an intermediate electrode seat facing the open end,a quantity ofcurrent-carrying fluid in the socket, a perspacing washers in stacked relationship in 'said open end adjacent the electrode with the per.-

forations `of' the electrode and washers in alignment forming a duct communicating with the v forated electrode on said seat, and perforated having'a channel formed with an opening at one end and'aseat facing said opening intermediate the ends of the channel, a perforated electrode in the seat, perforated spacing washers, in the channel between the electrode and the opening, said electrode and washers being supported with their perforations in alignment to form a duct be. tween' the open end and the channelportion extending on the side of the electrode opposite from the open end, another electrode sealed in the open end of the channel in position to close the end of the duct, and a quantity of current carrying fluid in said housing suilicient to fill the duct between the electrodes.

6. A circuit breaker of the character described comprising a housing having a channel, a pair of spaced electrodes in said channel, a plurality of plates having perforations and stacked in said` channel between said electrodes with said perforations in alignment to form a duct communi-I y eating with both electrodes, said channel form-- ing an expansion -space adjacentone of said electrodes, a liquid current-carrying medium in suf-.l

trical connection between said e1ectrodes.fsaid^.

7. A circuit breaker, asV setforth' in claim v6,

wherein at least one of said plates between the cient quantity to iill said duct and forman elec` electrodes comprises metallic material to which the liquid current carrying medium tends to adhere whereby to assist in retaining the medium in said duct Aunder normal conditions. Y

8. A circuit breaker as set forth in claim 6,

4wherein the perforations of at least one of said plates is of smaller dimension than the perforations in the other plates, said plate comprising highly arc-resistant material. t

9. A circuit breaker as set forth in claim 6, wherein one of said electrodes comprises a central electrode mounted in a Seat formed inter' mediate the ends of said channel and facing an `end thereof, the other electrode comprising an.

end electrode secured in the said end of the channel and the plates and central electrode be-` 'ing held in the channel in compression by and betweenthe end* electrode and the seat.

10. A circuit breaker as set forth in claim 6, wherein an annular element of conducting material is embedded in said housing in position exposed in the channel and forming a seat intermediate the ends of said channel and facing an end thereof, one of said electrodes comprising a perforated disc of conducting material and mounted in the seat formed by said annular element with the perforation of said disc in alignment with the perforations of said plates, the other electrode comprising an end electrode secured in the said end of the channel and the plates and central electrode being held in the channel in compression by and between the end electrode and the seat. l

FRANK J. McHUGH. 

